Abstract
Doping in semiconductors is a fundamental issue for developing high performance devices. However, the doping behavior in Si nanocrystals (Si NCs) has not been fully understood so far. In the present work, P-doped Si NCs/SiO2 multilayers are fabricated. As revealed by XPS and ESR measurements, P dopants will preferentially passivate the surface states of Si NCs. Meanwhile, low temperature ESR spectra indicate that some P dopants are incorporated into Si NCs substitutionally and the incorporated P impurities increase with the P doping concentration or annealing temperature increasing. Furthermore, a kind of defect states will be generated with high doping concentration or annealing temperature due to the damage of Si crystalline lattice. More interestingly, the incorporated P dopants can generate deep levels in the ultra-small sized (~2 nm) Si NCs, which will cause a new subband light emission with the wavelength compatible with the requirement of the optical telecommunication. The studies of P-doped Si NCs/SiO2 multilayers suggest that P doping plays an important role in the electronic structures and optoelectronic characteristics of Si NCs.
Highlights
On the other hand, light emission from Si nanocrystals (Si NCs) is an interesting topic because it can be potentially applied in the Si-based monolithic optoelectronic integrations[20,21,22]
Phosphorus-doped (P-doped) Si NCs/SiO2 multilayers were prepared by annealing amorphous P-doped Si/SiO2 stacked structures and the doping behaviors of P atoms were systematically studied by controlling the P doping concentrations and annealing temperatures
By the Raman and depth-profile X-ray photoelectron spectroscopy (XPS) measurements, it is demonstrated that P-doped Si NCs/SiO2 multilayers are obtained after annealing and P atoms are located in the Si layer or at the Si/SiO2 interface
Summary
Light emission from Si NCs is an interesting topic because it can be potentially applied in the Si-based monolithic optoelectronic integrations[20,21,22]. Though the indirect bandgap has excluded the bulk Si as a good choice for light emitting material, strong luminescence from the Si NCs has been reported owing to the enhanced radiative recombination probability of electron-hole pairs caused by the quantum confinement www.nature.com/scientificreports/. The quantum confinement effect will enlarge the bandgap of Si NCs compared to its bulk value (~1.1 eV), which causes the emission wavelength blueshift to the visible light region. It was reported that the subband light emission can be obtained in impurity-doped Si NCs, which provided a new approach to get the Si-based light emitter with the suitable wavelength[27,28]. The wavelength of the emission light meets the requirements of optical telecommunication, which makes P-doped Si NCs a potential material for the monolithic optoelectronic integrations
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